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Thursday, December 27, 2007

Tsunami Lessons for Sri Lanka

A. Severe damage, though inconsistent damage. At Peraliya, near to where the family had encountered those trucks with coral, the tsunami had swelled to a height of 30 feet and surged inland for more than a mile. There, it inundated a passenger train, the Ocean Queen, killing about 1,700 people. Yet, only three miles away, in Hikkaduwa, the wave came ashore with a height of about nine feet and barely grazed the beach. Why such differences?

I asked a fisherman at Peraliya, “Why was the inundation so severe right here?” He said, “Possibly the coral might be the issue, because this is largely a coral-mining area.”

From my fluid dynamics background, I knew he was making sense. If you take friction from a flow, it moves faster.

At Yala, where we’d stayed, I saw evidence of another type of beach-barrier destruction. The resort had been flattened to rubble; 175 people died there, including two friends from California. The owner told us how they’d taken down a sand dune so that all rooms could have an unobstructed view of the ocean. I returned to Arizona, convinced that human activity had magnified the disaster.

Q. So now you had a working theory. How did you prove it?

A. By employing a mixture of science and, believe it or not, journalism. A few weeks after I returned, the BBC asked me to consult on a documentary on the tsunami. With their funding, we hired divers to go underwater at eight different sites around the island, including Peraliya.

Q. In other words, you used this remarkable research technique — you looked!

A. Exactly. And the divers came back with pictures that were very clear. In the areas where there’d been a lot of inundation, there were no, or few, corals left.

Here at my lab at Arizona State, we have our very nice wave tank, which permits us to run waves at different speeds and heights and then measure the effects under controlled conditions.

So we made tsunami models with simulated coral reefs and then without them. What we saw was that where the coral was gone, the surging water increased by a factor of three or more.

At Princeton, Michael Oppenheimer’s research group took the idea further with sophisticated computer models, which substantiated my laboratory experiment. The research together has shown that when you cut down the coral reefs, or dunes or mangrove forests, you make a jetway for waves, because you have less bottom friction, and that lets the water through.

Q. Would you advocate a ban on coral mining?

A. Absolutely. Everywhere, not only in Sri Lanka. Once you start mining corals, you reduce beach defenses. If you have a tsunami or the more common event, a storm surge, the reef will help protect the land. ...

Q. Few scientists ever get to see their work have a direct impact on policy. What does that feel like?

A. I was born in Sri Lanka and I never thought I could make a contribution this way. I didn’t think I could do science that changed policy. Till the tsunami, I thought all I could do was to train students, which I did.

Of course, the research was associated with natural disaster, which is sad. But these are the types of problems that scientists should be helping with. Right now, I’m working a lot on the “heat island” effect, asking why air temperatures in cities like Phoenix and Colombo are about 8 degrees warmer than in surrounding areas. On a different project, funded by the U.S. Navy, we’re figuring out how wave action contributes to how land mines get buried in conflict areas. This can save a lot of lives. These are important questions, though they are also practical.

Many scientists are so engulfed in their own little area of fundamental research that they don’t want to directly embrace practical knowledge. That’s one barrier that I was able to break.